My attic gable fan (http://www.homedepot.com/buy/building-materials/ ceilings-attics/master-flow/power-gable-vent-pg3-1600-cfm-21356.html) has a thermostat built in that kicks on when it gets too hot up there. The fan is powered by a dedicated BX cable that runs up to the attic, and this cable has a regular wall switch that I can shut on/off from the 2nd floor hallway. I want the option to run the fan manually too, bypassing the thermostat. I can replace the BX calbe with a 4wire cable (two hot/one neutral/one ground), and have one of the wires bypass the thermostat.
But, what kind of wall switch would I need to buy that has, basically, three settings: off, on (for automatic fan operation via thermostat), and on (for manual operation of fan, bypassing thermostat)?
Advice appreciated. Thanks, Theodore.